Polymer Science, Series B最新文献

In this work, a good degree of epoxidation on poly(styrene)-b-poly(isoprene)-b-poly(styrene) (SIS) block copolymers containing different styrene content (15, 24, and 43%) has been achieved to get epoxidized SIS (eSIS). Thus, obtained eSIS has been blended with epoxy in different compositions. The role of styrene content on eSIS in generating the nanostructure on epoxy matrix has been carefully studied. The morphological findings have also been confirmed by dynamic mechanical analysis. Compared to other blend systems, a composition of 10 wt % eSIS having 24% styrene content is able to form a highly ordered nanostructure in the epoxy network with highest value of glass transition temperature (T_g). As the ratio of PS block in SIS increased, the plasticization effect due to the penetration of ePI block in the blends becomes less, which reflect in their T_g and thermal expansion coefficient (CTE). 10 wt % of eSIS having 43% styrene content largely reduces the CTE of epoxy matrix.

In this study, we aim to synthesize a novel hyperbranched unsaturated polyester resin nanocomposite based on graphene oxide using dicyclopentadiene maleate and poly methyl methacrylate-co-butyl acrylate. The incorporation of graphene oxide in the unsaturated polyester resin enhances the mechanical properties of the nanocomposite. Free radical copolymerization between double bonds of soya fatty acid, which is used to terminate the polyester and methyl methacrylate and butyl acrylate along with the reaction of dicyclopentadiene maleate with graphene oxide results in a three-dimensional cross-linked structure, allowing the unsaturated polyester resin to dry faster which makes it suitable for metal coating, especially car coating. The synthesized graphene oxide unsaturated polyester resin was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The results showed that the modified graphene oxide unsaturated polyester resin exhibited improved thermal stability and mechanical properties compared to the unmodified resin. This study provides a promising approach for developing high-performance nanocomposite materials using modified graphene oxide unsaturated polyester resin.

In order to improve the flame retardant and anti-melt-drip performance of PET fabrics in an environmentally friendly and simple way, two transparent phosphorus-containing silicone sols (DOPO-KH560,DOPA-KH602) based on 9,10-dihydro-9,10-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and silane coupling agents (KH560/KH602) were prepared and applied to the surface of PET fabrics using roll-baking process. The results of Micro Combustion Calorimeter (MCC) tests showed that the heat release capacity (HRC) and peak heat release rate (PHRR) of the DOPO-KH560 sol–gel finished fabric were reduced by 26 and 29% respectively. And the HRC and PHRR of the DOPA-KH602 sol–gel finished fabric were reduced by 35 and 46% respectively. The SEM and EDS results showed that the two silicone gel coatings were evenly distributed on the PET fabric. Thermogravimetric tests showed that both PET fabrics with silicone gel flame retardant exhibited higher charring rates at higher temperatures. Scanning electron microscopy of the residual char showed that both silicone gel flame retardant coatings promoted the formation of a rough char layer on the PET fabric. Based on the results of thermal cracking gas chromatography, Raman and X-ray photoelectron spectroscopy of the carbon residues, the mechanism of the flame retardant PET fabrics with the two silica gel coatings was investigated. This study provides a simple method to produce flame-retardant and drip-resistant PET fabrics using environmentally friendly chemicals through an already industrialized roll-drying process.

Phenolic fibers are a new type of heat-resistant organic fiber material prepared through spinning. They are made of phenolic resin and are spun and cured to obtain corrosion-resistant, high-temperature heat-insulating, smokeless, nontoxic fibers. Pure phenolic fibers have limitations in some applications due to their poor toughness and brittleness. Therefore, the improvement of the toughness of phenolic fibers and spinning has become the focus of research. In this work, phenolic fibers with an elongation at break of 8.7% and a breaking strength of 162.5 MPa were obtained by spinning epoxy-toughened phenolic resin. First, a high-ortho thermosetting phenolic resin solution (TPRS) was synthesized and blended with the phenolic epoxy resin F-44. Subsequently, as-spun fibers were prepared through dry-spinning. Finally, the as-spun fibers were subjected to microwave curing (MC). The effects of different TPRS : F-44 ratios and MC durations on the mechanical properties of the fibers were systematically investigated. Experimental results showed that under microwave conditions at a curing power of 80 W, the optimal mass ratio of TPRS : phenolic epoxy resin was 50 : 12 and the optimal curing time was 8 min. After the curing reaction, a large amount of hydroxymethyl groups was generated. During curing, the hydroxymethyl groups generated additional methylene bridges and epoxy groups underwent ring-opening reactions. Finally, a reticulated polymer was generated.

In this paper, tung oil-linseed oil (TO-LSO) and styrene-linseed oil (STY-LSO) were used as raw materials of sulfur-rich copolymers, which were then reversed vulcanized with S₈ at 130°C, and the gel time of the reaction was recorded. At the same time, ¹H NMR, DSC, XRD, sodium sulfite titration and other characterization methods were used to measure the reaction degree, verify the conjugated structure to improve the reaction degree, and study the synthesis mechanism of sulfur-rich copolymer. The results show that the conjugated structure can improve the reaction degree. And when the proportion of TO and STY is 20 and 10% respectively, the reaction gel time is shortened, the reaction degree is greatly deepened, and the effect of promoting polymerization can be significantly obtained. The synthesis mechanism of copolymer is the result of conjugated structure and diallyl group. The self-repair of sulfur-rich copolymers at different temperature and holding time by hot press shows that poly(20-TO-LSO-50S) can realize the S‒S bond self-repair after being compressed at 120°C for 4 h, and the surface of polymer disc was smoother and more uniform. However, poly(10STY-LSO-50S) can be repaired only after being compressed for 8 h. TO can not only enhance the synthesis process, but also enhance the performance of sulfur-rich materials and broaden the application field.

Conducting polymers with metal/metal oxide nanocomposites have recently attracted more attention from both the scientific sector and industry, with a focus on electrical and electromagnetic interference (EMI) shielding applications. Free-standing PPY-PVA/Ni (1, 2, 3, 4, and 5) ternary composite films were chemically synthesized by in situ chemical oxidative polymerization of pyrrole and polyvinyl alcohol (PVA, binder matrix) using ammonium persulfate as the oxidizing agent and coated with different concentrations (0.01, 0.02, 0.03, 0.04, and 0.05 M) of Ni⁺ ions using Adathoda vasica leaf extract as a reducing agent. The effect of PPY-PVA/Ni nanocomposites on the electrical and EMI shielding properties of nanocomposites was studied. The crystal structure of the dopant (Ni nanoparticles), thermal degradation and morphology of these composites were characterized by XRD, FESEM and TG analysis. The maximum electrical conductivity (4.2 × 10^–4 S/cm) was also achieved by doping PPY-PVA binary composites with 0.01 M Ni⁺ ions to form PPY-PVA/Ni-1 ternary nanocomposites. This significant increase in electrical conductivity achieves an EMI shielding effect of up to ~16.5 dB in the frequency range from 2.1 to 3 GHz (S-Band). An increase in electrical conductivity and EMI shielding for composites with hybrid fillers (PPY-PVA/Ni) demonstrates the synergistic benefits of such fillers when used together. Hence, these conducting polymers with metal/metal oxide nanocomposites could have the potential to be advantageous materials for technological applications.

Electrochemical behavior of hybrid electrodes with electroactive coatings based on activated IR-pyrolyzed polyacrylonitrile as well as hybrid polymer-carbon composites with activated IR-pyrolyzed polyacrylonitrile (porous N-doped carbon component) and poly(diphenylamine-2-carboxylic acid) (polymer component) has been investigated for the first time in a lithium-organic electrolyte (1 M LiClO₄ in propylene carbonate). Electrochemical behavior of the coatings has been investigated at a smooth glass carbon surface and at flexible strips of anodized graphite foil with developed porous loosened surface. Specific electrochemical capacity of the hybrid electrodes has been found dependent on the conditions of the composite coating synthesis. The influence of heat treatment on the electrochemical behavior of the activated IR-pyrolyzed polyacrylonitrile–poly(diphenylamine-2-carboxylic acid) composites has been investigated. Heat-resistant electroactive coatings have been obtained for the first time under conditions of IR heating of the IR-pyrolyzed polyacrylonitrile–poly(diphenylamine-2-carboxylic acid) composites, specific capacity of which in a lithium aprotic electrolyte has been 0.107–0.114 F/cm², only ~17% less than this for the starting composites at anodized graphite foil support, due to compaction of the electroactive layers hindering the electrolyte transport.

Efficiency and maintenance reduction in polymer nanocomposites are critical objectives for engineers and scientists to have an optimized machine component design. A crucial factor in achieving these goals is scratch resistance, which necessitates careful reinforcement selection for polymer composites. In this study, the individual nanofillers titanium dioxide (TiO₂) and graphene nanoplatelets (GnP) were morphologically characterized using electron microscopes, and molecular bonds analysis of epoxy-based hybrid nanocomposites was conducted using Fourier transform infrared (FTIR) spectroscopy. The amount of TiO₂ was kept constant at 2 phr (parts per resin) by weight, and GnP was varied as 0, 1, and 2 phr in the samples along with neat epoxy. A scratch adhesion test was performed, applying a constant and progressive load. The results indicate that an optimal combination of TiO₂ and GnP nanoparticles can enhance the scratch resistance properties of epoxy, as evidenced by favorable coefficients of friction (CoF) and scratch depths. Furthermore, optical and field emission scanning electron microscopes (FESEM) were employed to investigate scratch deformation in the nanocomposite samples. This article comprehensively reviews relevant literature, experimental details, significant findings, and a comparative analysis of scratch conditions in hybrid nanocomposites.

The interaction of the second-generation Grubbs catalyst and dimethyl maleate is investigated. It is shown that this interaction affords a new ruthenium-carbene complex capable of participating in the metathesis reaction. The metathesis homopolymerization of cyclooctene and 5-n-butyl-2-norbornene mediated by the first- or second-generation Grubbs catalyst in the presence of dimethyl maleate acting as a chain transfer agent is studied in detail. Conditions for the synthesis of previously unknown telechelic poly(5-n-butyl-2-norbornene) are optimized. The formation of heterodyads between the polyene block and dimethyl maleate fragments is revealed. Effect of the concentration of initial reactants, their ratio, accessibility of the main-chain double bond of polyene, catalyst type, temperature, and reaction time on the molecular weight and depth of the cross-metathesis reaction is explored. The efficiency of using dimethyl maleate as a chain transfer agent is demonstrated.

Double metal cyanide catalysts are unique heterogeneous catalysts having no alternative in the industrial polymerization of propylene oxide to produce poly(propylene oxide) with properties demanded for special-purpose applications: a low degree of unsaturation and high molecular weights and hydroxyl values. These catalysts are known since the 1960s, but academic publications addressing them started to appear only in the early 2000s, which coincided with interest in epoxide/CO₂ copolymerization and other catalytic processes. The present literature review aims to systematize information on the application of double metal cyanide catalysts in (co)polymerization reactions involving epoxides and other cyclic monomers. Much attention is paid to chemo- and regioselectivity issues and mechanistic aspects of epoxide/CO₂ copolymerization. Due to the use of ionic liquids and other homo- and heterogeneous catalyst in the reaction of epoxides and CO₂, double metal cyanide catalysts can be tuned for the selective synthesis of poly(ether carbonates), polycarbonates, or cyclic carbonates. Information on the application of these processes for the synthesis of functionalized (co)polymers is covered. Epoxide/cyclic anhydride copolymerization and epoxide/cyclic anhydride/CO₂ and epoxide/ε-caprolactone/CO₂ multicomponent reactions, including those using multicomponent catalytic systems based on the catalysts under consideration, are highlighted. Progress in this area suggests that double metal cyanide catalysts and multicomponent catalytic systems based on them will hold a prominent position in the synthesis of polymer materials of the future.